The present invention relates generally to testing a device using an automated tester, and more particularly to testing both the electrical and optical portions of the device.
Imaging devices are used in many of today""s consumer electronic products, as well as in various commercial and government applications. These imaging devices must be made as small as possible to facilitate use in portable products such as hand-held video recorders and the like. In order to make these imaging devices as small as possible, it is often desirable to include an optical sensor in the same package with associated electronic circuitry. Such an imaging device is shown in prior art FIG. 1.
In order to test an imaging device using an automated handler, for example an integrated circuit handler, the imaging device, for example imaging device 100, is normally positioned with electrical leads 102 pointing toward the test hardware such as is illustrated in orientation 111 of FIG. 1. Note that manufacturers often place the optical sensor 104, which may be an individual sensor or an array of sensors, on the top of imaging device 100 so that the optical sensor 104 is positioned away from the test hardware when electrical leads 102 are positioned for testing using automated handling equipment. An imaging device 100 oriented for electrical testing is shown in orientation 111, which is sometimes referred to as a xe2x80x9clive bugxe2x80x9d orientation because the integrated circuit package of imaging device 100 resembles a crawling bug.
Since the imaging device 100 includes an optical sensor 104, full parametric and functional testing of imaging device 100 requires the use of a controlled light source in addition to electrical test signals. These light sources are relatively large and are therefore usually placed inside of a test head (not shown) located beneath load-board/plate 105, where sufficient space is available. As a result, the light source cannot illuminate optical sensor 104 when imaging device 100 is positioned in a live bug orientation.
Consequently, in order to test the optical sensor portion of imaging device 100, imaging device 100 must be flipped over so that optical sensor 104 faces the test head and electrical leads 102 face away from the testing equipment as illustrated in orientation 120. The orientation of imaging device 100 shown in orientation 120 is sometimes referred to as a xe2x80x9cdead bugxe2x80x9d orientation because imaging device 100 resembles a bug lying on its back with its legs sticking up in the air.
One disadvantage of having to position the imaging device 100 in both live bug and dead bug orientations is that some package configurations cannot be properly positioned in both orientations using currently available integrated circuit handlers. Even where currently available integrated circuit handlers can properly position an image device in a dead bug orientation, extra positioning steps are required to completely and fully test devices having both optical and electrical portions. The requirement of extra positioning steps can add extra time and expense to the testing of devices such as imaging device 100.
Another factor to consider when testing devices in a dead bug orientation, is the need for more electrical connections to the handler. Extra connections are needed because in a dead bug orientation, the electrical pins face away from the tester, and signals must somehow be routed back to the tester. Normally these extra connections are provided by pogo pins, which sometimes fail and need to be replaced. For each electrical pin on the device being tested in dead bug orientation, two pogo pins are needed. Therefore, if a device to be tested includes eight electrical pins, sixteen pogo pins are required. Each of these sixteen pogo pins has a failure rate, and if any one of them fails the handler may be unusable until the pogo pin is replaced.
As should be apparent from the above discussion, currently available testing methodologies for devices including both optical and electrical portions are less than ideal, because fully automated testing can not be performed in some cases, and in other cases extra positioning steps are required to fully test imaging devices. What is needed is some way to permit testing of devices including both optical and electrical portions using a single device orientation.